Laser Melting, also referred to as laser sintering, is a well known method of manufacturing items from powder material, also called feedstock. The conventionally known laser sintering device has a sintering platform on which the item is built layer by layer by providing successive layers of feedstock wherein each layer is molten at selective regions of the layer by a laser beam.
The item to be manufactured is represented as a three dimensional computer model (hereinafter 3D model) for example a CAD (computer aided design) model. The 3D model is present as a series of sections divided in parallel planes disposed one upon the other. Each section contains information about a segment of the item to be manufactured.
In the conventional technique, on a surface of the sintering platform, a first layer of feedstock with a predetermined thickness, e.g. 20 to 40 micrometer is applied. Subsequently, a laser beam from a laser source scans over the surface of the first layer such that the feedstock melts and fuses together in selective regions of the first layer, i.e. where one wants to build the segment of the item. The regions where laser melting is performed are required to be located within an action area of the laser beam, i.e. where the laser beam can perform acceptable sintering by accurately and adequately melting the feedstock. Herein, the spatial extension of the action area is limited due to a limited scanning range of the laser beam. Thus, a first built segment corresponding to one section of the 3D model is obtained.
The sintering platform is then moved downwards and a second layer of the feedstock is applied. The surface of the second layer is located within the action area of the laser beam. The laser beam scans over the surface of the second layer to form a second built segment corresponding to a second section of the 3D model. Moreover, the scanning laser beam also results in fusing of the first build segment with the second built segment.
The method is similarly repeated for other successive sections of the 3D model. Thus, the laser sintering device forms the segments layer by layer of the feedstock. The surface of each successive layer of feedstock is located in the action area of the laser beam. In this way the entire geometry of the item is built up from the formation of successive built segments.
However, the conventional laser sintering as described above is useful for building an item with dimensions such that the surface of the item to be manufactured can be accommodated within the action area of the laser beam. For example, in conventionally known laser sintering techniques, the action area is approximately 250 by 250 mm square on surface of the feedstock layer applied. Thus, the sintering surface is limited heavily by action area of the laser beam. This drawback results from the laser beam deflection and is well known in the art of laser sintering. Attempting to sinter an object with a larger surface area on the feedstock layer results in degradation of the laser beam quality and the outcome is an inferior quality of item.